Common harrows are well known in the agricultural field. In more recent years rotary-type or active harrows are becoming more prevalent. The reason for this is that active or rotary-type harrows level the surface while leaving trash such as stubble or weeds on the surface. This is extremely beneficial in places such as the plains or prairies where wind erosion of soil has become a serious threat, particularly in dry years. Thus the use of active harrows is a consequence of a trend towards a no till or reduced till type farming operation.
Some known rotary harrows are towed such that the rolling axis is constrained, to an angle generally 20.degree. to 40.degree. from a line perpendicular to the direction of forward motion. This results in the drum being partially dragged longitudinally. This action causes the drum to rotate slower than if it were towed perpendicular to the direction of forward motion. Thus this angled rotation causes each tine to slip while in contact with the land surface,
The problem with rotary harrows is that they do not perform well in rocky soils. The tines of the harrow tend to break easily, and the longevity of the implement is greatly reduced. Another problem encountered with the rotary harrows is the difficulty of replacing the tines once they are broken. Some have complicated attachment mechanisms which are next to impossible for the average farmer to repair in the field. Obviously, if each time a tine breaks, it is necessary to call in a welder, the economics of the harrow are greatly diminished.
The use of resilient tines on harrows to promote deflection when the tines encounter obstacles is also known. For the most part however, these known rotary harrows have not operated satisfactorily- In rocky soils they tend to lack the force required to work the soil adequately.
It is therefore an object of the present invention to provide a rotary harrow which is durable and resists breakage of tines in rocky or stoney soils.
It is a further object of this invention to provide a harrow with tines which, when damaged, can be easily replaced by the operator in the field.
It is a further object of this invention to provide a rotary harrow with even tine penetration across the length of the drum.
Finally, it is an object of this invention to provide a rotary harrow which is particularly suited to clay soils and which, when in operation, deposits moisture laden lumps of clay from beneath the ground onto the surface, thus helping to curtail soil erosion.